drm/msm/mdp5: Remove direct access of dev->iommu_fwspec

Use the accessor functions instead of directly dereferencing
dev->iommu_fwspec.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20200326150841.10083-4-joro@8bytes.org

drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c

@@ -725,7 +725,7 @@ struct msm_kms *mdp5_kms_init(struct drm_device *dev)
 
 	if (config->platform.iommu) {
 		iommu_dev = &pdev->dev;
-		if (!iommu_dev->iommu_fwspec)
+		if (!dev_iommu_fwspec_get(iommu_dev))
 			iommu_dev = iommu_dev->parent;
 
 		aspace = msm_gem_address_space_create(iommu_dev,